交互网站开发,建设局网站更改法人所需材料,网片价格,APP客户端网站建设JDBC中Statement接口本身不能直接操作BLOB数据类型
操作BLOB数据类型需要使用PreparedStatement或者CallableStatement(存储过程) 这里演示通过PreparedStatement操作数据库BLOB字段 设置最大传入字节 一般是4M 可以通过以下命令修改 set global max_allowed_packet1024*1…JDBC中Statement接口本身不能直接操作BLOB数据类型
操作BLOB数据类型需要使用PreparedStatement或者CallableStatement(存储过程) 这里演示通过PreparedStatement操作数据库BLOB字段 设置最大传入字节 一般是4M 可以通过以下命令修改 set global max_allowed_packet1024*1024*32; 这里封装的方法本身就可以对Blob字段进行 存 取
数据库 实体类 JDBC的封装类
package com.utils;import java.lang.reflect.Field;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;
import java.util.ResourceBundle;/*** author hrui* date 2023/10/13 13:49*/
public class DBUtils {private static ResourceBundle bundleResourceBundle.getBundle(jdbc);private static String driverbundle.getString(jdbc.driver);private static String urlbundle.getString(jdbc.url);private static String usernamebundle.getString(jdbc.username);private static String passwordbundle.getString(jdbc.password);static{try {Class.forName(driver);} catch (ClassNotFoundException e) {e.printStackTrace();}}//通用查询多个public static T ListT selectList(ClassT clazz, String sql, Object...args){Connection connnull;PreparedStatement psnull;ResultSet rsnull;try {connDBUtils.getConnection();psconn.prepareStatement(sql);for(int i0;iargs.length;i){ps.setObject(i1, args[i]);}rs ps.executeQuery();ResultSetMetaData metaData rs.getMetaData();int columnCount metaData.getColumnCount();ListT listnew ArrayList();while(rs.next()){T t clazz.newInstance();for(int i0;icolumnCount;i){Object object rs.getObject(i 1);//String columnName metaData.getColumnName(i 1); 这个方法返回实际列名String columnLabel metaData.getColumnLabel(i 1);//该方法返回别名,没有别名就返回列名columnLabel getString(columnLabel);Field field clazz.getDeclaredField(columnLabel);field.setAccessible(true);field.set(t,object);}list.add(t);}return list;} catch (Exception e) {e.printStackTrace();}finally {DBUtils.closed(conn,ps,rs);}return null;}private static String getString(String columnLabel) {if (columnLabel.contains(_)) {int index columnLabel.indexOf(_);String replace columnLabel.replace(_, );char c Character.toUpperCase(replace.charAt(index));columnLabel replace.substring(0, index) c replace.substring(index 1);}return columnLabel;}//通用查询单个public static T T selectOne(ClassT clazz,String sql,Object...args){Connection connnull;PreparedStatement psnull;ResultSet rsnull;try {connDBUtils.getConnection();psconn.prepareStatement(sql);for(int i0;iargs.length;i){ps.setObject(i1, args[i]);}rs ps.executeQuery();ResultSetMetaData metaData rs.getMetaData();int columnCount metaData.getColumnCount();if(rs.next()){T t clazz.newInstance();for(int i0;icolumnCount;i){Object object rs.getObject(i 1);//System.out.println(object.getClass());String columnLabel metaData.getColumnLabel(i 1);columnLabel getString(columnLabel);Field field clazz.getDeclaredField(columnLabel);field.setAccessible(true);field.set(t,object);}return t;}} catch (Exception e) {e.printStackTrace();}finally {DBUtils.closed(conn,ps,rs);}return null;}public static Connection getConnection() throws SQLException {Connection connection DriverManager.getConnection(url, username, password);return connection;}//通用增删改方法public static int update(String sql,Object...args){Connection conn null;PreparedStatement psnull;int count0;try {conn DBUtils.getConnection();ps conn.prepareStatement(sql);for(int i0;iargs.length;i){ps.setObject(i1, args[i]);}count ps.executeUpdate();//ps.execute();} catch (SQLException e) {e.printStackTrace();}finally {DBUtils.closed(conn,ps,null);}return count;}public static void closed(Connection conn, Statement st, ResultSet rs){if(rs!null){try {rs.close();} catch (SQLException e) {e.printStackTrace();}}if(st!null){try {st.close();} catch (SQLException e) {e.printStackTrace();}}if(conn!null){try {conn.close();} catch (SQLException e) {e.printStackTrace();}}}}用工具类中封装的方法 存 取 下面详解下PrepareStatement单独存取数据库Blob字段
有很多方法 读取 像下面这样也行 这样就保存文件了
